1. Field of the invention
The present invention relates to an aliphatic polyester resin composition containing plasticizers, and sheets, films or other products molded by the resin.
2. Description of the Background Art
In recent years, attention has focused on biodegradable plastics which reduce environmental load as a result of increased awareness regarding problems to the human body and natural environment. Examples of biodegradable plastics on which attention has been focused include an aliphatic polyester. Though a polylactic acid as the aliphatic polyester itself is an inherently brittle resin, however flexibility can be applied by adding plasticizers thereto. The application development of polylactic acid has been briskly performed in recent years, and various novel plasticizers capable of being used for the polylactic acid and having a low environmental load have also been proposed.
Though triethylene glycol diacetate, glycerin triacetate, glycerin tripropionate, tributyl acetylcitrate, etc., have been known as plasticizers which apply flexibility with the transparency of the polylactic acid maintained (for example, refer to Patent Reference 1), any of plasticizers and polylactic acid are not sufficiently compatible. When applications to various uses are actually attempted, the increase in the amount of additional plasticizers causes intense bleed out generated from the resin of the plasticizers before obtaining sufficient flexibility, and thereby the increase is not suitable for practical use.
Though a producing method of stretched film made of flexible aliphatic polyester by adding a diaceto monoglyceride fatty acid ester and a polyglycerol monoaliphatic ester as the plasticizer which does not bleed has been known (for example, refer to Patent Reference 2), when the application to a packaging material is attempted using the composition of this technique, sufficient flexibility and transparency are acquired. However, there is a problem that the amount of elution of the plasticizers is large in an elution test due to a paraffin solvent, and correspondence is further desired on a use condition where the plasticizers come into contact with oily food.
The present inventors have previously proposed the use of diacetomonoglyceride fatty acid ester and polyglycerin acetic acid ester as the plasticizers (for example, refer to Patent Reference 3). However, also in the composition, the problem of a shift of the plasticizers to food has not been completely solved.    Japanese Published Unexamined Patent Application No. Hei-11-323113    Japanese Published Unexamined Patent Application No. 2000-302956    Japanese Published Unexamined Patent Application No. 2003-73532